Motor controller
A motor controller controlling a rotational speed of a motor and including a thermal detector, a capacitor, an operational amplifier (OP), a charging/discharging circuit, a flip-flop and a logic circuit. The thermal detector detects environmental temperature of the motor to set a first reference voltage. The capacitor has one terminal coupled to a second reference voltage while another terminal thereof is charged/discharged by the charging/discharging circuit, controlled by a pulse width modulation (PWM) signal, to provide a third reference voltage. The OP compares the first and third reference voltages and outputs the comparison result to a ‘set’ terminal of the flip-flop. The flip-flop further uses a ‘reset’ terminal to receive a clock signal and the output signal thereof is utilized in generating the PWM signal. The PWM signal is further provided to the logic circuit for setting a duty cycle of a driving current of the motor.
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This Application claims priority of Taiwan Patent Application No. 099134853, filed on Oct. 13, 2010, the entirety of which is incorporated by reference herein..
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to motor controllers, and in particular relates to motor control techniques controlling a radiator fan.
2. Description of the Related Art
With the shrinking size of electronic components, an increased quantity of electronic components may be contained in an electronic device generating considerable thermal energy. Thus, heat dissipation is an important issue in the design of electronic devices. Using a radiator fan is a well-known solution.
Generally, a radiator fan is driven by a motor, and the rotational speed of the radiator fan depends on a driving current of the motor. To save energy, the rotational speed of the radiator fan may be adjusted according to the environmental temperature. The technique of using a proper driving current to rotate a radiator fan according to the environmental temperature to dissipate heat has been a significant topic in the field.
BRIEF SUMMARY OF THE INVENTIONMotor controllers are disclosed to control a rotational speed of a motor. The motor may be utilized to rotate a radiator fan.
A motor controller in accordance with an exemplary embodiment of the invention comprises a thermal detector, a first capacitor, a first operational amplifier, a charging/discharging circuit, a flip-flop and a logic circuit. The thermal detector detects environmental temperature to dynamically determine a first reference voltage. The first capacitor has a first terminal coupled to a second reference voltage and has a second terminal coupled to the first operational amplifier to provide the first operational amplifier with a third reference voltage. The charging/discharging circuit charges/discharges the first capacitor based on a pulse width modulation signal, such that that the third reference voltage vibrates accordingly. The first operational amplifier compares the third reference voltage with the first reference voltage and outputs a comparison result to a set terminal of the flip-flop. A reset terminal of the flip-flop receives a clock signal and a signal at an output terminal of the flip-flop is utilized in the generation of the pulse width modulation signal. In addition to controlling the charging/discharging circuit, the pulse width modulation signal is utilized by the logic circuit to determine a duty cycle of a driving current of the motor, to thereby determine the rotational speed of the motor.
In the application of a radiator fan, the disclosed motor controller allows the radiator fan to adjust the rotational speed thereof according to the environmental temperature, so as to optimize power efficiency.
A detailed description is given in the following embodiments with reference to the accompanying drawings.
The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description shows several embodiments carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
The elementary structure of the motor controller 100 includes a thermal detector 104, a first capacitor C1, a first operational amplifier OP1, a charging/discharging circuit 106, a flip-flop 108 and a logic circuit 110. The thermal detector 104 detects the environmental temperature of the motor 102, to dynamically determine the value of a first reference voltage V1(T), where the parameter T represents the environmental temperature, and, the thermal detector 104 may be a thermistor or any electronic device operating according to the environmental temperature.
The first reference voltage V1(T) is coupled to the first operational amplifier OP1; for example, the first reference voltage V1(T) may be coupled to an inverting input terminal (labeled ‘-’) of the first operational amplifier OP1. The first capacitor C1 has one terminal coupled to a second reference voltage V2, and has another terminal coupled to the charging/discharging circuit 106, controlled by a pulse width modulation signal PWM, to provide a third reference voltage V3. The charging/discharging circuit 106 charges/discharges the first capacitor C1 and thereby the third reference voltage V3 vibrates accordingly. The third reference voltage V3 is coupled to the first operational amplifier OP1; for example, the third reference voltage V3 is coupled to a non-inverting input terminal (labeled ‘+’) of the first operational amplifier OP1. By the first operational amplifier OP1, the vibrating third reference voltage V3 is compared with the temperature-dependent first reference voltage V1(T), and the compassion result is outputted to a set terminal of the flip-flop 108 (e.g. a terminal ‘S’ of an SR flip-flop). The flip-flop 108 further has a reset terminal (e.g. a terminal ‘R’ of an SR flip-flop) receiving a clock signal CLK and has an output terminal (e.g. a terminal ‘Q’ of an SR flip-flop).
In the embodiment of
Because the rotational speed of the motor 102 is dependent on the duty cycle of the driving current I thereof, the disclosed elementary structure of the motor controller controls the rotational speed of the motor 102 according to the environmental temperature. In a high temperature environment, the radiator fan rotated by the motor 102 rotates at a higher speed in comparison with a low temperature environment. The power efficiency is optimized.
The embodiment of
The following discussion, references the time indexes t1, t2 and t3. At the time index t1, the clock signal CLK is enabled. The reset terminal a′ of the flip-flop 108 detects the enabling of the clock signal CLK and thereby resets the signal ‘
The pulse width modulation signal PWM is switched to low accordingly. Controlled by the high ‘
To summarize, the enable cycle TP1 of the pulse width modulation signal PWM depends on a time interval required to raise the third reference voltage V3 to the first reference voltage V1(T). In other words, the temperature-dependent first reference voltage V1(T) determines the duty cycle TP1/TP2 of the pulse width modulation signal PWM and thereby determines the rotational speed of the motor 102. For example, the first reference voltage V1(T) may be a positive coefficient of the environment temperature. The higher the environmental temperature is, the greater the first reference voltage V1(T) is, and the longer the time interval is required to raise the third reference voltage V3 to the first reference voltage V1(T). In this manner, the enable cycle TP1 of the pulse width modulation signal PWM is increased so that the motor 102 is sped up and the rotational speed of the radiator fan is increased. On the contrary, the lower the environmental temperature is, the lower the first reference voltage V1(T) is and the shorter the time interval is required to raise the third reference voltage V3 to the first reference voltage V1(T). In this manner, the enable cycle TP1 of the pulse width modulation signal PWM is decreased, so that the motor 102 slows down and the rotational speed of the radiator fan is decreased. Therefore, the rotational speed of the radiator fan is adjusted according to the environmental temperature. The power efficiency is optimized.
In the following paragraphs, another adjustable parameter—the cycle period, TP2, of the pulse width modulation signal PWM—is discussed to control the duty cycle TP1/TP2 of the pulse width modulation signal PWM. The cycle period TP2 of the pulse width modulation signal PWM is dependent on the cycle period of the clock signal CLK. To control the length of the cycle period TP2 of the pulse width modulation signal PWM, a clock signal generating circuit is introduced.
Referring to
The third current source I3 is operative to generate a third current (labeled “I3’ as well) to be coupled to the second capacitor C2 by the sixth switch SW6 for discharging the second capacitor C2. The second operational amplifier OP2 compares the voltage levels at the non-inverting terminal ‘-’ and the inverting terminal ‘+’ thereof, to output the clock signal CLK to the flip-flop 108. To oscillate the clock signal CLK, the third, fourth, fifth and sixth switches SW3, SW4, SW5 and SW6 are controlled by the feedback of the clock signal CLK. The third and fifth switches SW3 and SW5 are turned on when the clock signal CLK is disabled (i.e., controlled by the inverted clock signal ‘
According to the design of the clock signal generating circuit 114, the oscillation period TCLK of the generated clock signal CLK is:
Because the cycle period TP2 of the pulse width modulation signal PWM approximates the oscillation period TCLK of the clock signal CLK (i.e. TP2≅TCLK), the length of the cycle period TP2 of the pulse width modulation signal PWM may be determined by properly designing the components—including C2, R1˜R3, I2 and I3—of the clock signal generating circuit 114. In this manner, the duty cycle TP1/TP2 of the pulse width modulation signal PWM can be determined and thereby the rotational speed of the motor 102 can be determined.
In some embodiments, the first and second capacitors C1 and C2 have identical capacitances (C1=C2), the sum of the resistance of the first and third resistors R1 and R3 equals to the resistance of the second resistor R2 (for example, R1=R3=0.5R2 so that R1+R3=R2), and the second and third currents I2 and I3 are identical (I2=I3). The calculation for the time interval TP1 required to charge the third reference voltage V3 from the second reference voltage V2 to the first reference voltage T1(T) is:
and the calculation for the duty cycle TP1/TP2 of the pulse width modulation signal PWM is:
Because, C1=C2, R1+R3=R2 and I2=I3, the calculation of the duty cycle TP1/TP2 of the pulse width modulation signal PWM may be simplified as:
The relationship between the duty cycle TP1/TP2 and the first reference voltage V1(T) depends on the design of the first current source I1, the second current source I2 and the second reference voltage V2; thus, the relationship between the rotational speed of the motor and the variation of the environmental temperature may be determined.
respectively,
where Vbp represents a bandgap reference voltage. The resistance of the first and second reference resistors Rref1 and Rref2 are designed by the user and may be deployed outside of the chip so that they may be conveniently replaced by resistors of other resistances.
Combined with the design of FIG. 3—I1=Vbg/Rref1 and I2=Vbg/Rref2—equation (1) may be simplified as:
In the application of a radiator fan, the duty cycle TP1/TP2 of the pulse width modulation signal PWM determines the rotational speed of the radiator fan and the first reference voltage V1(T) is dependent on the environmental temperature. The relationship between the environmental temperature and the rotational speed of the radiator fan may be shown as the curve 402 of
Referring back to
This paragraph discusses the operations of the driving current setting circuit formed by the switches SW7˜SW10. If the hall effect sensed by the hall effect sensor shows that the driving current should flow in the first direction 504, then, the seventh and the eighth switches SW7 and SW8 should be turned on/off according to the enabling/disabling of the pulse width modulation signal PWM. On the contrary, if the hall effect sensed by the hall effect sensor shows that the driving current should flow in the second direction 506, then, the ninth and the tenth switches SW9 and SW10 should be turned on/off according to the enabling/disabling of the pulse width modulation signal PWM. In this manner, the rotational speed of the radiator fan controlled by the motor 502 is adjusted according to the environmental temperature. The logic controlling the switches SW7˜SW10 are provided by the logic circuit 110 shown in
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Claims
1. A motor controller controlling a motor, comprising
- a thermal detector for detecting environmental temperature around the motor to dynamically determine a first reference voltage based on the detected environmental temperature;
- a first capacitor having a first terminal and a second terminal, wherein the first terminal is coupled to a second reference voltage;
- a first operational amplifier coupled to the second terminal of the first capacitor to receive a third reference voltage and compare the third reference voltage with the first reference voltage;
- a charging/discharging circuit charging/discharging the first capacitor based on a pulse width modulation (PWM) signal to change the third reference voltage;
- a flip-flop having a set terminal receiving a signal at an output terminal of the first operational amplifier, a reset terminal receiving a clock signal, and an output terminal coupled to the charging/discharging circuit to provide the charging/discharging circuit with the PWM signal; and
- a logic circuit coupled to the output terminal of the flip-flop to determine a duty cycle of a driving current of the motor based on the PWM signal.
2. The motor controller as claimed in claim 1, wherein:
- the first reference voltage is coupled to an inverting input terminal of the first operational amplifier;
- the third reference voltage is coupled to an non-inverting input terminal of the first operational amplifier; and
- a signal at the output terminal of the flip-flop is regarded as the inverted signal of the PWM signal.
3. The motor controller as claimed in claim 2, wherein the charging/discharging circuit comprises:
- a first current source for providing a first current;
- a first switch coupled between the first terminal and the second terminal of the first capacitor, which is turned on when the PWM signal is disabled; and
- a second switch coupled between the first current source and the first switch, which is turned on when the PWM signal is enabled to conduct the first current to charge the first capacitor.
4. The motor controller as claimed in claim 1, further comprising a clock signal generating circuit, wherein the clock signal generating circuit comprises:
- a second operational amplifier having a non-inverting input terminal, an inverting input terminal and an output terminal outputting the clock signal;
- a resistor series having a first resistor, a second resistor and a third resistor sequentially coupled between a voltage source and a ground, wherein a connection node between the first and second resistors provides a fourth reference voltage, and a connection node between the second and the third resistors provides a fifth reference voltage;
- a third switch turned on when the clock signal is disabled and coupled to the fourth reference voltage to the inverting input terminal of the second operational amplifier;
- a fourth switch turned on when the clock signal is enabled and coupled to the fifth reference voltage to the inverting input terminal of the second operational amplifier;
- a second capacitor coupled to the non-inverting input terminal of the second operational amplifier;
- a second current source and a third current source for providing a second current and a third current, respectively;
- a fifth switch turned on when the clock signal is disabled to conduct the second capacitor charge through the second current; and
- a sixth switch turned on when the clock signal is enabled to conduct the second capacitor discharges through the third current.
5. The motor controller as claimed in claim 4, wherein:
- the first capacitor and the second capacitor have identical capacitance;
- the resistance of the first resistor and the third resistor equals to the resistance of the second resistor; and
- the second current equals to the third current.
6. The motor controller as claimed in claim 4, wherein:
- the first current source includes a first reference resistor and generates the first current based on the resistance of the first reference resistor; and
- the second current source includes a second reference resistor and generates the second current based on the resistance of the second reference resistor.
7. The motor controller as claimed in claim 6, wherein the first reference resistor and the second reference resistor are disposed outside of a chip form consisting essentially of the motor controller for convenient replacement.
8. The motor controller as claimed in claim 1, further comprising:
- a hall effect sensor for sensing a status of the motor to determine a flow direction of the driving current of the motor.
9. The motor controller as claimed in claim 1, further comprising a driving current setting circuit, wherein the driving current setting circuit comprises:
- a seventh switch coupled between a first terminal of the motor and a voltage source;
- an eighth switch coupled between a second terminal of the motor and a ground;
- a ninth switch coupled between the second terminal of the motor and the voltage source; and
- a tenth switch coupled between the first terminal of the motor and the ground,
- wherein the driving current of the motor flows in a first direction when the seventh and the eighth switches are turned on, and
- wherein the driving current of the motor flows in a second direction when the ninth and the tenth switches are turned on.
10. The motor controller as claimed in claim 9,
- Wherein the PWM signal is provided so that turn on the seventh and the eighth switches when a sensed result of a hall effect sensor shows that the driving current of the motor flows through the first direction; and
- Wherein the PWM signal is provided so that turning on the ninth and the tenth switches when the sensed result of the hall effect sensor shows that the driving current of the motor should flows through the second direction.
7659678 | February 9, 2010 | Maiocchi |
Type: Grant
Filed: Oct 12, 2011
Date of Patent: Oct 29, 2013
Patent Publication Number: 20120091936
Assignee: Princeton Technology Corporation (New Taipei)
Inventor: Chi-Lin Hsu (New Taipei)
Primary Examiner: Bentsu Ro
Assistant Examiner: David Luo
Application Number: 13/271,596
International Classification: G05D 23/20 (20060101); H02K 29/08 (20060101);